Pump out drill bit



Feb. 251, 1969 c. c. BRQWN 3,429,387

PUMP OUT DRILL BIT Filed March 6, 1967 Sheet 1 of 2 A TTO/PNEV Feb. 25,1969 c. c. BROWN 3,429,387

PUMP OUT DRILL BIT Filed March 6, 1967 Sheet 2 of 2 29 ll L @26 Z/ Z7 2328 24 6 4 2 22 l 23 I] H a c/cmo a ROWN INVE TOR.

A T TORNE) 3,429,387 PUMP OUT DRILL BIT Cicero C. Brown, Brown OilTools, Inc.,

R0. Box 19236, Houston, Tex. 77024 Filed Mar. 6, 1967, Ser. No. 620,807US. Cl. 175237 Int. Cl. EZlb 9/22, 23/04 9 Claims ABSTRACT OF THEDISCLOSURE Background of the invention In many operations in connectionwith the drilling of oil and gas wells, it is often necessary to performvarious types of operations in the well bore, many of which may betermed repair operations" which involve placing cement plugs in the wellcasing to seal up leaks or improperly located perforations. These mustthen be followed by drilling out the cement plug and reperforating orperforming other operations necessary or appropriate to the proceduresinvolved.

In conventional operations of the type described, a series of runs withdrill pipe, tubing, or wire line strings must be made to introduce thesuccessive forms of tools required to perform the several operationswhich may be involved. Each time a string of pipe carrying well tools isrun into and out of a well, a considerable amount of time is involvedwhich can be very expensive, particularly where the operations must beconducted at great depths as is often the case.

For example, in a not uncommon situation where a well casing has beenperforated at a location which does not communicate with the producingformation, it is necessary to shut-off these perforations andre-perforate at the correct locations. Closing off of the undesiredperforations is generally done by packing-off the well bore at properpoints and placing a body of cement in the well bore at a location suchas to plug the incorrectly located perforations. Very often this is doneunder pres sure to squeeze oflf the perforations. This operationrequires the running of a string of pipe and other equipment, as may berequired for placing the cement, and this equipment must then be removedfrom the well bore. Thereafter, as soon as the cement has hardened adrilling string carrying a drill bit must be run back into the well todrill out the cement plug to clear the bore hole. This string must thenbe withdrawn from the well and replaced by a pipe or wire line stringcarrying a perforating gun to re-perforate the casing at the properlocation.

Thus, it will be seen that several trips, requiring running andwithdrawing pipe strings, must be made into and out of the well bore tocomplete the series of operations outlined above, all of whichnecessarily require a substantial amount of time which, in aconventional deep well drilling operation, is very costly.

Summary of the invention The present invention is directed to animproved form of drill bit which may be carried into a well bore on adrill string and is constructed to permit carrying out a series ofoperations, such as those described above, with 3,429,387 Patented Feb.25, 1969 the same pipe string without having to withdraw the drillstring from the well bore during the performance of the severaloperations involved.

In accordance with the present invention the drill bit comprises atwo-part structure consisting of a main bit which includes a tubularbody connectible in the usual manner to the lower end of a drill string,and carrying full-gauge cutters and a pilot bit including a tubularshank carrying pilot cutters. The two-sets of cutters are arranged anddimensioned to cover the cross-sectional area of the bore hole to bedrilled thereby. The shank of the pilot bit is coaxially inserted in thebore of the main bit and secured thereto by releasable means.

The releasable means may be of any suitable and known form, such asshear pins or latches, which are re leasable in response to a relativedownward force applied to the shank of the pilot bit. This downwardforce is provided by dropping a ball or other conventional pluggingdevice through the pipe string carrying the bit to seat on and plug theshank of the pilot bit. Thereupon, application of pump pressure todrilling fluid or other fluid in the pipe string will develop thehydraulic force necessary to actuate the release means to release thepilot bit and expel it from the bore of the main bit. This action willclear the bore of the main bit body. As the bore of the main bit body,in accordance with this invention, is preferably made to substantiallythe same diameter as the bore of the pipe string, a full bore passagewill be provided through the pipe string and bit for movement of varioustools into the well bore below the bit for con ducting the desiredoperations.

Other and more specific objects and advantages of this invention willbecome more readily apparent from the following detailed descriptionwhen read in conjunction with the accompanying drawing which illustratesusefu embodiments in accordance with this invention.

In the drawing:

FIG. 1 is a view, partly in elevation and partly in section, of a bit inaccordance with one embodiment of this invention, the bit being shown inassembled condition for drilling;

FIG. 2 is a view similar to FIG. 1, showing the pilot bit being expelledfrom the main bit;

FIG. 3 is a lower end view of the bit of FIG. 1 as viewed upwardly fromline 3-3 of FIG. 1;

FIG. 4 is a view similar to FIG. 1 of an alternate embodimentillustrating a modified form of the releasable connection means betweenthe pilot and main bits;

FIG. 5 is a view similar to FIG. 4, showing the pilot bit being expelledfrom the main bit; and

FIG. 6 is a cross-sectional view taken generally along line 6-6 of FIG.4.

Referring first to the embodiment illustrated in FIGS. 1 to 3, the bitconsists of a two-part structure comprising a main bit, designatedgenerally by the numeral 1, and a pilot bit, designated generally by thenumeral 2.

The main bit comprises a tubular body 3 having an internally threadedbox 4 at its upper end for attaching the bit to a conventional drillpipe string (not shown), and having an axial bore 5 which willpreferably be made to the same internal diameter as the pipe string towhich the bit is attached. Body 3 carries a plurality of angula-rlyspaced, radially extending cutting blades 6 terminating at their lowerends in hard-surfaced teeth 7.

Pilot bit 2 comprises a tubular shank 8, having an axial bore 9, whichis slidably receivable in the lower end of bore 5 of the main bit and issecured thereto by suitable releasable means, such as conventionalfrangible shear pins 10. A seal packing 11 is arranged in a packinggroove 12 provided about the exterior of shank 3 adjacent its upper endto sealingly engage the wall of bore 5. The lower end of shank 8 carriesa plurality of angularly spaced, radially extending cutting blades 13having cutting teeth 14 at their lower ends. The upper ends 15 of blades13 are receivable in correspondingly shaped slots 16 provided in thelower end of body 3 of the main bit and function as keys for locking themain and pilot bits against relative rotation to thereby relieve shearpins from torsional forces which would otherwise be exerted between themain and pilot bits. The pilot bit will be oriented relative to the mainbit so that blades 13 of the pilot bit will be angularly interspersedwith blades 6 of the main bit. The angular spaces between blades 13 ofthe pilot bit define passages 17 (FIG. 3) through which fluid my bedischarged from the pipe string to which the bit is attached. The upperend of shank 8 surrounding bore 9 may be bevelled at 18 to provide aseat for sealing engagement by a plugging element such as a ball 19,which may be delivered from the surface through the pipe string carryingthe bit.

The arrangement of the cutting blades of the main and pilot bits is suchas to enable the composite structure to drill out a hole to the fulldiameter of the circle defined by outer edges of blades 6 of the mainbit which determine the gauge of the bit. The blades 13 and teeth 14 ofthe pilot bit will cover the center portion of the circular area cut bythe bit.

By way of example of one application of the bit in accordance with thisinvention, it will be assumed that it is desired to plug off improperlyplaced perforations in a well casing and to then re-perforate the well.

The bit, constructed as described herein, will be attached to a stringof drill pipe and run into the well bore to a point above the improperperforations. Cement may now be introduced through the pipe string,passages 17 provided in the bit permitting the drill pipe string to beused as a cementing string. When the cement has been placed, the pipestring will be elevated only enough to raise the bit clear of the cementbody, or excess cement adjacent the bit may be circulated out inaccordance with conventional practices, and the cement allowed toharden. The drill pipe string carrying the bit having been retained inthe well bore, it is now employed to drill out the cement plug touncover the section of the well wall which is to be re-perforated. Fluidwill be circulated through the pipe string and the well bore in theusual manner during this drilling operation.

When the hole has thus been cleared, a plugging device such as ball 19will be dropped into the pipe string and pumped down to engage seat 18and plug bore 9. Thereupon, application of pump pressure to the fluid ontop of ball 19 will be increased to a pressure great enough to breakshear pins 10, whereupon the pilot bit will be expelled bodily from bore5 of the main bit providing a full bore opening through the bit.

Now it becomes possible to lower a perforating gun of conventionaldesign on a suitable operating string, which may be either a wire lineor small diameter pipe or cable, through the bore of the pipe string andbore 5 of the main bit into position for perforating the well wall asdesired. When this operation has been completed, the drill pipe stringcarrying the main bit may be withdrawn and production pipe run, ifdesired, or the drill pipe string may be left in the well bore as theproduction string should that prove desirable.

It will be understood that in operations such as described, the pipestring may also carry packers and other devices commonly used in sealingoff sections of the bore hole to permit pressurizing or squeezing thecement.

As may be seen from the foregoing, the employment of a bit in accordancewith this invention, permits the performance of a plurality ofoperations in a well bore without requiring a multiplicity of runs intoand out of the well bore of pipe strings as conventionally required forperforming the sequence of operations heretofore described.

The bit may, of course, be used for conventional drilling operations andeither or both the main and pilot bits may be equipped with thewell-known and conventional rotary cutters instead of the blade cuttersillustrated and described herein.

FIGS. 4 to. 6 illustrate a modification in which the releasable meanssecuring the pilot bit to the main bit is in the form of latching dogsheld and released by a mandrel slidably positioned in the bore of theshank of the pilot bit.

Referring to FIGS. 4 to 6, the releasable connection means includes aplurality of angularly spaced latches 20 disposed for radial movement incorrespondingly shaped openings 21 in the wall of shank 8. The dogs areshaped to be projected outwardly of shank 8 into an annular latchinggroove 22 provided in the wall of bore 5 of the main bit. The innerfaces of latches 20 carry vertically spaced, inwardly projecting lugs 23-23. A release sleeve or mandrel 24 is slidably mounted in bore 9 of thepilot bit shank and carries outwardly projecting vertically spaced lugs25 positioned to register with lugs 23 at one position of the mandrel(FIG. 4) which will hold latches 20 in projected latching position ingroove 22. Mandrel 24 is initially secured in this position by means ofshear pins which extend through the wall of main bit body 3 and the wallof pilot bit shank 8 adjacent its upper end. Thus shear pins 110initially secures shank 8 to the main bit and also secures mandrel 24 inthe locking position. A seal packing, such as an O-ring 26, is mountedin a groove 27 about the exterior or mandrel 24 to seal with the wall ofbore 9 of the pilot bit shank. Mandrel 24 has an axial bore 28 whichwill allow fluid flow through passages 15 of the bit. The upper end ofbore 28 terminates in a bevelled seat 29 for engagement by a pluggingdevice such as ball 19.

The latching arrangement illustrated in FIGS. 4 to 6 is of a known form,one example of which is illustrated in U.S. Patent No. 3,115,188, andthe details thereof do. not, therefore, form a part of this inventionbut are illustrated and described as an example of another form ofreleasable connection means between the main and pilot elements of thebit herein described.

In operation of the modification illustrated in FIGS. 4 to 6, when ball19 is dropped on to seat 28 and fluid pressure applied thereto, theinner end portions of shear pins 110 which extends between shank 8 andmandrel 24 will first be severed allowing mandrel 24 to be shifteddownwardly relative to shank 8 to the position shown in FIG. 5, at whichlugs 25 will move out of registration with and into interspersedrelation to lugs 23. This will free latches 20 for movement inwardly ofmandrel 24 and out of groove 22. The pressure on mandrel 24 will now betransmitted through the interspersed lugs to shank 8 and the increasingdownward force exerted by the fluid through mandrel 24 will break theportions of shear pins 110 Which extend between body 3 and shank 8,thereby releasing the latter to permit expulsion of the pilot bit fromthe bore of the main bit, as seen in FIG. 5. Seals 11 and 26 willprevent leakage of pressure fluid during application of fluid pressureto ball 19 after it is seated.

It will be understood that other modifications and changes may be madein the details of the illustrative embodiments within the scope of theappended claims but without departing from the spirit of this invention.

What I claim and desire to secure by Letters Patent is:

1. A drill bit, comprising, a main bit attachable to a drill string andincluding a body having an axial through bore, a pilot bit including atubular shank coaxially inserted in said bore and adapted to be pluggedby a plugging element passed through said drill string, and releasablemeans connecting the pilot bit to said body, said means being releasableby fluid pressure exerted through said bore when said shank has beenplugged whereby to expel the pilot bit from the bore of the main bit,said releasable means comprising: latch elements mounted for radialmovement through the wall of said shank, a latching groove in the wallof said bore positioned for engagement with said latch elements, and atubular mandrel mounted in the bore of said shank for longitudinalmovement between one position holding said latch elements in latchingengagement with said groove and a second position releasing said latchelements for movement out of said groove.

2. A drill bit according to claim 1 including annular seal meansarranged between said shank and the Wall of said bore.

3. A drill bit according to claim 1, wherein said releasable meanscomprises frangible shear pins.

4. A drill bit according to claim 1 including means additional to saidreleasable means carried by said main and pilot bits for initiallylocking said bits against rotation relative to each other and operableto be released upon release of said releasable means.

5. A drill bit according to claim 4, wherein said additional meanscomprise cooperating longitudinally engaged key-and-slot elements.

6. A drill bit according to claim 1, wherein said main and pilot bitscarry cooperating cutter elements constructed and arranged to drill abore hole of predetermined diameter.

7. A drill bit according to claim 6, wherein the cutter elements on eachof said bits comprise a plurality of angularly spaced, longitudinallydisposed, radially extending blades, and wherein the blades on the pilotbit are angularly offset with respect to those on the main bit.

8. A drill bit according to claim 7, wherein the upper ends of theblades on said pilot bit form keys slidably receivable in complementaryslots in the lower end of said body of the main bit whereby to lock themain and pilot bits against relative rotation.

9. A well drilling bit comprising, a main bit including a tubular bodyhaving an axial bore, a pilot bit having a tubular shank extendingcoaxially into the bore of said body, and releasable means securing saidshank to said body and releasable therefrom in response to fluidpressure exerted through said bore when said bore is plugged to expelthe pilot bit from said bore, whereby to provide a full bore openingthrough said main bit to permit passage therethrough of other welltools, said releasable means comprising: latch elements mounted forradial movement through the wall of said shank, a latching groove is thewall of said bore positioned for engagement with said latch elements,and a tubular mandrel mounted in the bore of said shank for longitudinalmovement between one position holding said latch elements in latchingengagement with said groove and a second position releasing said latchelements for movement out of said groove.

References Cited UNITED STATES PATENTS 2,793,833 5/1957 Daniel 17512,883,154 4/1959 Daniel l1 2,890,861 6/1959 Cook 1 X 2,902,094 9/1959Nelson et al 175317 DAVID H. BROWN, Primary Examiner.

US. Cl. X.R. l75392, 412

